(1) Field of the Invention
The present invention relates to a process for treating used frying oil or fat (further collectively referred to as cooking oil or oil) from frying operations, such as industrial frying operations and restaurants, in order to remove impurities from the cooking oil, restore its odor, color and other characteristics and thus make it possible to reuse the oil extending its service life.
(2) Description of Related Art
There is a large number of restaurants in the United States. These facilities employ large quantities of cooking oil for frying potatoes, sea food, chicken and many other food items for immediate consumption. Another mammoth demander of cooking oil is a food industry where food is prepared, packaged, and shipped in mass quantities for future consumption. Since frying oil decomposes over time and use due to the formation and acquisition of various contaminants during cooking, its continuous use, no matter how economically justified and attractive it may be, is inadmissible without removing those contaminants.
Disclosed in U.S. Pat. No. 5,391,385 of J. Seybold is a process for treating cooking oil containing contaminants comprising the steps of heating the oil to a temperature of 180° F. to 400° F., contacting the oil with a composition consisting of a mixture of 60% to 80% amorphous silica and 20 to 40% alumina for a time sufficient to remove contaminants from the oil; and separating the composition from the oil. The amorphous silica is selected from the group consisting of silica gel, precipitated silica and fumed silica, and the alumina is selected from the group consisting of activated alumina, calcined alumina, hydrated alumina, precipitated alumina, pseudoboehmite, bayerite and gamma alumina. The amorphous silica is preferably a hydrogel, the alumina is preferably a hydrated alumina, and the composition contains 70% of silica hydrogel and 30% of hydrated alumina.
Known from U.S. Pat. No. 6,187,355 of C. Akoh et al. is a method of treatment and recovery of used frying oils that employs combinations of adsorbents and antioxidants such that the recovered frying oil can be reused. Used frying oil is treated with a ternary mixture of adsorbents comprising calcium silicate, magnesium silicate and at least one of a porous rhyolitic material and silicon dioxide in effective amounts to reduce free fatty acids of the treated used frying oil as well as improve total polar component, oil stability and color thereof. Combinations of antioxidants can be included in the treated oil in effective amounts to improve oil stability and service life of the treated used frying oil.
U.S. Pat. No. 6,368,648 of B. Bertram et al. also discloses a method of treating used cooking oil. The process provides for passing the used cooking oil from a used cooking oil source to a holding vessel, and contacting the used cooking oil with a predetermined amount of purifying material (such as amorphous hydrous precipitated synthetic magnesium silicate) upon accumulation of a first predetermined amount of the oil in the holding vessel. The used cooking oil and the purifying material are then passed from the holding vessel to a filter apparatus upon accumulation of a second predetermined amount of the oil in the holding vessel. The second predetermined amount of oil is greater than the first predetermined amount. Upon passing of the used cooking oil and the purifying material from the holding vessel to the filter apparatus, the purifying material becomes entrained in the filter apparatus. The used cooking oil is then passed from the filter apparatus to the source. After the oil is treated, residual oil and the used purifying material may be removed from the filter apparatus by blowing gas through the filter apparatus.
Also known is a method of decolorization, deodorization and deoxidation of cooking oil comprising filling a porous container with a mixture of plant-based granulated activated carbons and a natural antioxidant material, filtering used oil through a filter to remove food particulates and solids, and storing the porous container with the mixture in the oil (U.S. Patent Application Publication 2008/0102181A1 of R. Rao et al.) The plant-based granulated activated carbons comprises nutshell based granulated activated carbons, and the natural antioxidant material comprises lemon peel.